Whoever gave you this problem clearly expects you to know that the area of triangle ABC is given by \frac{1}{2}\left|\vec{AB}\times \vec{AC}\right|. ...
Good to start with but in 2009 Anna's age is A+ 3 so "Anna is half of Becky's age" is A+ 3= (B+ 3)/2 and "Mary is six years older than Anna" is M+3=...
The crucial point in your previous post was that, after squaring both sides of \sqrt{a^2+ b^2}= a+ b, to get x^2+ b^2= a^2+ 2ab+ b^2, the "a^2+ b^2"...